Reaction Steps
Ethanol (0.975 L) was added to iron powder (62.5 g, 1.12 mol) under nitrogen atmosphere. Concentrated HCl (9.03 mL) was added at ambient temperature and the suspension was heated to 65° C. for 1.5 h. The suspension was then cooled to 50° C., and sat. aq. NH4Cl (299 g) were added. The temperature of the reaction mixture was allowed to reach 50° C., and (4aS,5S,7aS)-7a-(2-fluoro-5-nitrophenyl)-5-(trifluoromethyl)-4a,5,7,7a-tetrahydro-4H-furo[3,4-d][1,3]thiazin-2-amine hydrochloride (75.0 g, 187.0 mol) was added in portions while maintaining temperature below 68° C. After 30 min, ethanol (0.45 L) was added, and the reaction mixture was cooled to 20-25° C. over 1 h. The suspension was stirred for 2 h and filtered over Celite (75 g) rinsing with ethanol (0.972 L). The solution was concentrated under vacuum to a brown solid. Water (0.9 L) was added followed by 3.0 N NaOH (0.187 L, 560 mmol) while maintaining temperature below 35° C. The resulting suspension was stirred for 1 h at 20-25° C. The suspension was filtered, and the solid was rinsed with cold water (0.38 L). The solid was dried under vacuum at 40-45° C. over 24 h to obtain the title compound (57.7 g, 95.5%). 1H NMR (500 MHz, DMSO) δ ppm 6.81 (dd, J=12.5, 8.6 Hz, 1H), 6.62 (dd, J=7.0, 2.9 Hz, 1H), 6.50-6.42 (m, 1H), 6.16 (s, 2H), 4.96 (s, 2H), 4.72-4.54 (m, 1H), 4.35 (d, J=7.8 Hz, 1H), 3.74 (dd, J=7.8, 2.5 Hz, 1H), 3.18-3.08 (m, 1H), 3.01 (dd, J=13.9, 3.0 Hz, 1H). 2.84 (dd, J=13.8, 3.8 Hz, 1H); 13C NMR (125 MHz, DMSO) δ ppm 156.20 (d, JCF=243.0 Hz), 148.73, 145.49, 127.86 (d, JCF=11.0 Hz), 116.79 (d, JCF=24.8 Hz), 116.10 (d, TCF=3.3 Hz), 114.10 (d, JCF=8.0 Hz), 78.89, 76.57 (q, JCF=31.0 Hz), 66.35, 36.35, 23.11.
